1. Technical Field
The present invention relates to an ultrasonic diagnostic apparatus, and in particular, to a technique for evaluating or measuring conduction of an electric signal in the heart.
2. Background Art
An ultrasonic diagnostic apparatus is an apparatus which forms an ultrasonic image based on a reception signal obtained by transmitting and receiving ultrasound to and from a living body. The ultrasonic diagnostic apparatus generally comprises a probe, a transmitting unit, a receiving unit, an image forming unit, a measuring unit, etc. The concept of the ultrasonic diagnostic apparatus in the present application also includes a computer having an ultrasonic image processing function.
In the human heart, contraction of a cardiac muscle is caused by an electric signal generated in the living body stimulating the cardiac muscle. The electric signal is transmitted in the heart from a sinus node via a plurality of routes to the entirety of the heart. The contraction timings of the right atrium, the left atrium, the right ventricle, and the left ventricle do not match each other. That is, there is a time difference in the motions of the individual cardiac muscle sites in the heart. It can be deduced that, by evaluating such a time difference, it is possible to identify abnormality of the motion of the cardiac muscle or cardiac disease. However, the ultrasonic diagnostic apparatuses of the related art are not equipped with a function to measure such a conduction time difference or a contraction time difference. For the heart of a fetus in the mother's womb, direct measurement of the electrocardiographic signal is difficult. There is desire for a method in which the conduction of the electric signal can be measured for the heart of a fetus.
JP 2007-75333 A discloses an ultrasonic diagnostic apparatus having a function to track an observation point designated by a user by applying a pattern matching (image matching) technique between adjacent frames. The tracking is two-dimensional tracking.
As described, there is desire to measure conduction of the electric signal in a heart (in particular, the heart of a fetus). This is because a cardiac muscle motion is primarily observed with the eyes on a two-dimensional tomographic image (video image) of the heart and it is difficult to identify abnormality of an electric signal conducting system or abnormality of the cardiac muscle motion. In order to diagnose a disease of the heart, it is desired to objectively or quantitatively evaluate such abnormality.